Semiclosed cycle gas laser system

ABSTRACT

A flowing gas laser system of the mixing type removes lasing gas from the laser effluent so as to recycle the remaining gas, such as a mixture of energizing gas and relaxant gas. Fresh lasing gas is introduced into the system from a pressurized source thereof. Typically, carbon dioxide is removed from the laser effluent so as to permit reuse of a mixture of helium and nitrogen, by means of a lithium oxide or lithium hydroxide solid absorbent bed which is cooled by expanded CO2 from the liquefied source. In one embodiment, the liquid CO2 also precools the main gas flow prior to entrance into the CO2 adsorber. The warmed CO2, with or without additional external heat supplied thereto, is passed through an expander, which operates a turbine to drive a compressor used for creating flow through the system. The CO2 which leaves the expander at temperatures of about 0* F. is then divided into two streams. One stream may be used to precool the laser effluent gases prior to reaching the compressor inlet as well as cool the laser chamber, while the other stream is used directly in the laser chamber. An excess of CO2 may be flowed through all of the above-described processes by venting some of it to ambient, and using only part of it as the lasing gas, or a part of the CO2 may be passed directly from the liquefied source into the laser chamber. A second embodiment employs a prime mover to drive the flow-inducing compressor, the liquid CO2 being expanded and passed directly into the laser chamber at a very low temperature or serving to remove heat from the CO2 adsorber, prior to its use as a lasing gas. External coolants are provided so as to cool the adsorbent or pre- and post- cool the laser effluent as it moves through a compressor, thereby maintaining the size of the compressor and the power requirements thereof quite small. Electrical power may be generated on the compressor drive shaft in either embodiment. The latter embodiment may employ readily available electrical power to run an electric excitation power supply, and even a small electric motor to drive the compressor.

United States Patent Melikian et al.

[ 51 Mar. 7, 1972 [54] SEMICLOSED CYCLE GAS LASER SYSTEM [72] Inventors:Gorken Melildan, Springfield, Mass;

Frank ll. Bianeardi, Vernon, Conn.

[73] Assignee: United Aircraft Corporation, East Hartford, Conn.

[22] Filed: Sept. 10, 1969 [21] Appl.No.: 858,566

[52] US. Cl ..33ll94.5, 330/43 [51] int. Cl ..li0ls 3/09, l-lOls 3/22,HOls 3/04 [58] Field ofSearch ..33l/94.5;330/4.3

[56] References Cited UNITED STATES PATENTS 3,391,281 7/1968 Eerkens..33 1194.5 X 3,435,363 3/1969 Pate] ..331/94.5

Primary ExaminerRonald L. Wibert Assistant Examiner-R. J. WebsterAltomey-Melvin Pearson Williams ABSTRACT A flowing gas laser system ofthe mixing type removes lasing gas from the laser effluent so as torecycle the remaining gas, such as a mixture of energizing gas andrelaxant gas. Fresh lasing gas is introduced into the system from apressurized source thereof. Typically, carbon dioxide is removed fromthe laser effluent so as to pennit reuse of a mixture of helium andnitrogen, by means of a lithium oxide or lithium hydroxide solidabsorbent bed which is cooled by expanded CO, from the liquefied source.in one embodiment, the liquid CO, also precools the main gas flow priorto entrance into the CO, adsorber. The warmed C0,, with or withoutadditional external heat supplied thereto, is passed through anexpander, which operates a turbine to drive a compressor used forcreating flow through the system. The CO, which leaves the expander attemperatures of about 0 F. is then divided into two streams. One streammay be used to precool the laser effluent gases prior to reaching thecompressor inlet as well as cool the laser chamber, while the otherstream is used directly in the laser chamber. An excess of CO, may beflowed through all of the above-described processes by venting some ofit to ambient, and using only part of it as the lasing gas, or a part ofthe CO, may be passed directly from the liquefied source into the laserchamber. A second embodiment employs a prime mover to drive theflow-inducing compressor, the liquid C0, being expanded and passeddirectly into the laser chamber at a very low temperature or serving toremove heat from the CO, adsorber, prior to its use as a lasing gas.External coolants are provided so as to cool the adsorbent or preandpostcool the laser effluent as it moves through a compressor, therebymaintaining the size of the compressor and the power requirementsthereof quite small. Electrical power may be generated on the compressordrive shaft in either embodiment. The latter embodiment may employreadily available electrical power to run an electric excitation powersupply, and even a small electric motor to drive the compressor.

13 Claims, 4 Drawing Figures #097 i 2 Ida/F66 4% $7 l 4-Zi PatentedMarch 7, 1972 3,,1Q4

2 Sheets-Sheet 1 SEMICLOSED CYCLE GAS LASER SYSTEM BACKGROUNDOF THEINVENTION l. Field of Invention This invention relates to flowing gaslasers of the mixing type, and more particularly to a semiclosed cyclesystem therefor.

22. Description of the Prior Art It is known in the art to product laserradiation in a flowing gas laser which introduces the laser gas inproximity with the laser cavity separately from the excited energizinggas. In such systems, it is necessary to supply separate sources oflasing gas and energizing gas to the laser chamber. The energizing gasmay have mixed therewith a relaxant gas. A typical system of this typeemploys carbon dioxide as a lasing gas, nitrogen as an energizing gas,and helium as a relaxant. There are a wide variety of attractiveapplications for self-contained highpower laser units, such as mobileflowing gas laser apparatus. However, such apparatus must include storedfuel and consumables. It is thus attractive to minimize the amount ofstored consumables and fuel required. Fuel is consumed by the primemover to drive the compressor which provides flow through the system,and therefore conservation of fuel suggests that the inlet temperatureof a compressor be kept as low as possible. It is also known that theperformance of a gas laser would be enhanced with low-input gastemperatures. Additionally, it is impractical to provide lightweight,highly efficient prime movers of small size. Thus, there are a number offunctional requirements for self-contained flowing gas lasers of themixing type which mitigate against the operation of closed-cycle systemswithout provisions for cooling and refrigeration as well as circulationand separation of the laser gases.

SUMMARY OF INVENTION The object of the invention is to provide animproved flowing gas laser system of the mixing type.

According to the present invention, lasing gas is removed from theeffluent of a flowing gas laser of the mixing type, and the remaininggases are recycled through the laser; fresh lasing gas is introduced.According still further to the present invention, a high-pressure sourceof liquefied lasing gas is used to cool the CO adsorption apparatusprior to the use of this gas or additional CO, gas as the lasing gas inthe laser. In ac' cordance with further aspects of the presentinvention, the lasing gas may be flowed through heat exchangers prior tointroduction into the laser chamber so as to improve overall laser cycleoperation. In further accord with the invention, excess lasing gas maybe vented to ambient so as to permit a greater flow through the heatexchange element of the lasing gas adsorption apparatus and various heatexchangers than the flow required for operation of the laser itself. Inaccordance with the invention still further, the flowing lasing gas maybe utilized to drive the flow-inducing compressor, thus obviating theneed for a prime mover or a source of fuel. Further, heat may be addedto the flow of lasing gas so as to increase its work-producing capacitywhere system demands so require. The broadest aspects of the inventionmay be incorporated in a system utilizing a prime mover, with a highlyconservative use of stored low enthalpy lasing gas directly in the laseror to cool the lasing gas adsorption apparatus prior to passage into thelaser system.

The present invention permits recycling of energizing and relaxantgases, while introducing fresh lasing gas from a source. This simplifiesthe separation process since the lasing gas need not be recovered, butsimply removed from the main stream of laser effluent gas. Additionally,utilization of the low enthalpy (heat sink capacity) of pressurized,liquefied lasing gas eliminates the need for other heat sinks or forfuel, and permits operating a selfcontained flowing gas laser system ofthe mixing type at low-input laser gas temperatures, a minimum of storedconsumables and/or fuel, and with lowpressure losses.

The foregoing and other objects, features and advantagesof the presentinvention will become more apparent in the light of the followingdetailed description of preferred embodb ments thereof, as illustratedin the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 through 4 are simplifiedschematic diagrams of semiclosed cycle flowing gas laser systems of themixing type in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. I, a gaslaser 10 includes an optical cavity having mirrors 12, I4 into which isinjected a lasing gas, such as carbon dioxide, by means of an injectingrod or spray bar 16. Also a mixture of energizing and relaxant gases(such as nitrogen and helium) are flowed through a high-voltage DCelectric discharge plasma, or other excitation means 18, into the lasercavity. The excitation means 18 is connected by wires 20 to a powersupply 22 which is supplied power by wires 24 from an electric generator26. Useful optical power may be extracted through one of the mirrors,such as mirror I2.

The energizing and relaxant gases are supplied by a conduit 28 from aCO, adsorption apparatus 30 which may comprise a lithium oxide orlithium hydroxide bed arranged preferably in the form of a disposablecartridge. The adsorption of CO, into such a bed is exothermic, so heatmay be removed from the reaction within the CO, adsorption apparatus 30by a heat exchange element 32 which is supplied a cold mixture of liquidand gaseous CO, from an expansion valve 34 that is connected to a tank36 of pressurized liquid C0,. The expansion valve 34 expands the liquidCO, from the source 36 so as to provide it in a mixed liquid-gaseousflow at very low temperatures. The low temperatures will be maintainedeven though a great amount of heat is absorbed into the flow due to theheat required for vaporization of the flow. Since the temperature canremain extremely low (on the order of 60 F the size of all the heatexchangers through which this flow may pass (described hereinafter) fora given rate of heat exchange, can be much smaller than they would be ifthe liquid CO, were not brought to a lower temperature by expansion. Inother words, if the liquid CO, were released from the tank withoutexpansion, it would maintain the same temperature that it had assumedwhile pressurized (say ambient, about 70 P.) so that even though itcould absorb vast quantities of heat, it would do so only at 70 andwould be vaporizing at 70. Thus it could remove heat only from fluids ata much higher temperature, or at a somewhat higher temperature withlarge heat exchangers.

In the embodiment of FIG. I, the CO; becomes gaseous as it passesthrough the heat exchange element 32, due to the heat it absorbs as aresult of the exothermic CO, adsorption reaction. It should be notedthat CO, which has passed through the laser is adsorbed by theadsorption apparatus 32, and fresh CO, is utilized to cool thisapparatus. All of the CO, which is eventually adsorbed in the apparatus30 has previously passed through the heat exchanger 32. The gaseous CO,is passed by a conduit 34 to a heat exchanger 36a where it removes heatfrom the main flow of laser effluent in a duct 38, to thereby cool theeffluent before it passes through a duct 40 to the CO, adsorptionapparatus 30. From the heat exchanger 36a, a duct 42 carries the CO, toa heater 44. The heater 44 may supply no heat, a little heat, or a lotof heat to the CO, as is necessary, in dependence upon the powerrequirements of a turbine 46 to which the heater is connected by a duct48. The turbine 46 drives a shaft 50 which may be utilized to drive theelectric generator 26 and the compressor 52 which causes the necessaryflow of gases through the system. Because the low-pressure energizingand relaxant gases are circulated in a closed loop there is no need tocompress these gases to atmospheric pressures or higher. This being so,the compressor 52 can be much smaller and consume much less power thanwould be true if the laser effluent were vented to atmosphere. This isone of the primary advantages of the present invention.

The CO expands to a pressure somewhat above atmospheric and cools (toperhaps F.) as it passes through the turbine 46, and is then separatedinto two streams, one of which is then conducted by a conduit 54 to aheat exchanger 56. In the heat exchanger 56, the temperature of the CO,is raised by removing heat from the main laser etfluent supplied theretoby a conduit 58, so that as it is conducted to the compressor inlet by aconduit 60, it is at a reasonably low temperature, thereby avoiding anunduly large compressor 52. From the heat exchanger 56, the conduit 64carries the CO, to a heat exchange element 70 which is in the thermalcommunication with the main structure of the laser 10, and removes wasteheat therefrom, thus lowering the total enthalpy and temperature of theefi'luent in the conduit 58. A valve 72 permits exhausting the heatexchanger 70 to ambient pressure.

The other portion of the CO, in the conduit 54 is passed through anexpansion valve 74 to reduce its pressure from approximately atmosphericto approximately that of the laser chamber. The gas is then passedthrough a conduit 76 to the spray bar 16, where the CO enters the lasercavity at a low temperature and produces laser radiation in a fashionknown to the art.

Operating conditions of the embodiment of FIG. 1 must all relate to therequired nominal operating conditions of the gas laser 10. The flow ofenergizing and relaxant gases dirough the energizing means I8 should beat about l00 F. or lower and at a pressure of roughly 50 to 75 Torr.Thus, the outflow of these gases from the CO adsorption apparatus 30should be at low pressure and at about l00 F. If the pressure is nototherwise suitable, an expansion valve may be inserted in the conduit28. The temperature, however, is readily adjusted since the heatexchange element 32 may be so designed and proportioned to reach thattemperature, the temperature of mixed liquid and gaseous CO therethroughbeing sufficiently low. For instance, the source 36 of liquid CO may beat about 60 atmospheres, and it may be reduced in the expansion valve 34to about atmospheres. Since the expanded, semigaseous CO, has atemperature in the neighborhood of -60 F., there is an extremely goodheat exchange capability to remove not only residual heat in the flowwithin the conduit 40 as it enters the adsorption apparatus, but alsoall of the heat generated as a result of adsorbing the C0,.

By properly sizing the heat exchanger 70, the laser cavity can bemaintained at a temperature commensurate with an effluent temperature inthe conduit 58 of about 400 F. This is cooled in the heat exchanger 56to approximately 100 F., thus minimizing the power requirements and sizeof the compressor 52 and turbine 46. As the mixture of nitrogen, heliumand C0 is compressed, it may be pumped up to between 120 and I50 Torr,at a temperature of between 240 F. and 340 F. The heat exchanger 360 canreduce this to 125 to 150 F. provided that the temperature of thegaseous CO in the conduit 34 is around 100 to 125 F. As beforedescribed, extra heat in the gases within the conduit 40 as well as theheat of adsorption can be removed from the CO adsorption apparatus 30 sothat its outflow is at around l00 F.

The CO leaving the heat exchanger 36a in the conduit 42 may be atroughly 200 F. However, a typical installation may require the CO in theconduit 48 at a temperature of between 270 F. and 370 F. in order to getsufficient work out of the turbine 46 to drive the generator 26 and thecompressor 52. In such a case, the heater 44 can consume some smallamounts of fuel to raise the relatively low flow of gaseous CO, to thishigher temperature, In cases where a relatively small system isutilized, or where it is desirous to eliminate the heater and any fueltherefore, an excess amount of CO, may be utilized, thus increasing theconsumption of C0, and therefore the amount of CO which must be storablein the system. The excess CO can be accommodated by being passed throughthe heat exchanger 70 at the gas laser I0, and thence to ambientpressure. After expansion, the CO, in the conduit 54 may be at atemperature of between F. and +40 F., so that a portion of this gas iscapable of good heat exchange with the hot effluent (400 F.) of thelaser in the conduit 58 within heat exchanger 56. As the CO, leaves theheat exchanger 56 in conduit 64, it may have a temperature somethingunder l00 F so that it is still capable of a good heat exchangerelationship in the heat exchanger 70. The remaining CO, from theturbine exhaust may be introduced to the spray bar l6 for use in the gaslaser 10.

A variation of the embodiment of FIG. 1, shown in FIG. 2 may utilize aportion of the CO, outflow of the storage container 36 to supply thespray bar I6 directly through a reducing valve 35, and the remainder ofthe CO, is passed through a valve 34 into the heat exchanger element 32,thereby cooling the adsorber 30. From the adsorber 30, the stream of CO,is then passed through a conduit 34 to a heat exchanger 36a, and then toa heat exchange element 70a. Further heating of this flow is conducted,as necessary, in the heat source 44, prior to passage of the flowthrough conduit 48 to the expander 46 and then through conduit 54 to theheat exchanger 56. This excess CO is finally exhausted to ambientpressure through a valve 57.

This embodiment consumes a slightly increased amount of C0 but has alower fuel consumption, the C0, being supplied at an increasedtemperature to the heat source 44, and provides a lower temperature C0,feed directly to the spray bar I6. Thus, the overall performance of thelaser system is improved.

A further modification of the invention is illustrated in FIG. 3.Therein, as the gaseous CO leaves the heat exchanger 36a in a duct 42b,it is supplied directly to a heat exchanger 70 before being passed overa duct 48a to the turbine expander 46. The heat exchanger 70 alsoreceives efiluent of the laser in the duct 58 and passes it over theduct 60 to the compressor 52. Thus, the heat required in the CO, inorder to impart sufl'lcient energy to drive the turbine expander 46(with the electric generator 26 and compressor 52 as loads) is allsupplied by the heat-sinking capability of the pressurized liquid CO,(36) and the heat imparted to the CO, by the heat exchangers 30, 36a and70. In this embodiment, the spray bar I6 is directly connected through aconduit 72 to the turbine-expander 46, and there is no heat exchanger onthe jacket of the gas laser 10.

The embodiments of FIGS. 1 and 3 are particularly well suited to systemswherein a high concentration of CO, is desired in the laser gas flow,and a high flow rate per unit of optical power or to systems requiringless work be performed by the compressor 52. In FIG. 3, CO, is conservedsince excess thereof is not required as a coolant for the gas laserjacket. Also, although shown in FIG. 3 with no heat source, it should beunderstood that a heat source such as the source 44 could readily beinserted within the conduit 480 if necessary in order to supplysufficient energy to the turbine-expander 46 in order to satisfy theload requirements of the system.

A second embodiment of the invention is illustrated in FIG. 4. The maindistinction between this and the embodiments of FIGS. 1 through 3 isthat a prime mover 76 drives a shaft 78 for operating the electricalgenerator 26 and the compressor 52. In this embodiment, the CO is fedthrough pressurereducing valves directly into the laser I0 or utilizedto cool the adsorption apparatus 30 and to operate the gas laser I0. TheCO, pressure may be maintained above 5.l l2 atmospheres in the conduit34a to prevent the formation of solid C0, prior to expansion of the CO,through the spray bar I6. In order to keep the size of the prime mover76 as small as possible, a heat exchanger 80 may be utilized to cool theeffluent of the laser 10 within the conduit 58, so that the inlettemperature of the compressor 52 will not be too high. Additionally, aheat exchanger 82 may cool the main flow of gas as it leaves thecompressor 52 so as to remove the heat of compression therefrom prior topassing the gas through the C0, adsorption apparatus 30. The adsorber 30is cooled by an externally supplied coolant passing through heatexchanger 32. Further, an additional option may employ the CO, 36 tomaintain the adsorber 30 at a moderate temperature prior to beingintroduced into the spray bar 16. This is desirable since commonadsorption material such as lithium oxide and lithium hydroxide do notfunction well if the inlet gas is allowed to go much over to lSO F.However, the heat exchange element 32 tends to keep the apparatus coolsince the coolant enters the heat exchange element 32 at roughly 60 to100 F.

The heat exchangers 32, 80, 82 may be supplied water or other coolantfrom a source 84 which may be any suitable source (such as tap water ora nearby stream) or may in fact comprise a portion of an air-cooled,pumped coolant system, as is known in the art. This embodiment utilizesa minimum of C0,, since flow is provided by the prime mover.

The prime mover 76 in the embodiment of FIG. 4 may comprise a smallgasoline engine, since the work required to operate the compressor 52 isminimal, there being only small pressure drops across the adsorptionmaterial 30 and through the heat exchangers 80, 82. On the other hand,the embodiment of FIG. 4 may be modified if a suitable source ofelectrical power is available. The source of electrical power may takethe place of the electric generator 26 and in fact provide power to anelectric motor which could be substituted for the prime mover '76 aswell as power for the power supply 22. Thus, a self-contained system,rely ig only on a source of elec trical power can be also achie\ .d withthe embodiment of FIG. 4. A further alternative to the embodiment shownin FIG. 4 could provide an expander attached to shaft 78 which woulddevelop power to help drive the compressor 52 and generator 26. Such anexpander could be driven by the CO, from source 36 preheated by passagethrough the adsorber 30 and heat exchangers 80 and 82. This variation ofthe FIG. 4 embodiment would reduce the required prime mover power, fuel,and coolant flow, of the system, at the expense of additional componentsand complexity.

Thus, the present invention provides the singular advantage, to aflowing gas iaser of the mixing type, of permitting selfcontainedoperation utilizing only a source of pressurized liquid laing gas, orsuch source together with small amounts of fuel or electric power. Theenergizing and relaxant gases are cycled, since carbon dioxide isremoved therefrom in a very simple fashion. The pressure drops throughthe system are much lower than a system in which separation oflasing gasresults in recovery thereof for further use, thus mitigating the amountof energy which has to be imparted into the system in order to maintainlaser operation. Further, the invention incorporates use of the cold CO,directly as the lasing gas or to cool the C0 separator, and in certainembodiments to cool laser gas effluent at various points in the cycle.The present invention is capable of being implemented in a variety offashions, and although it has been shown and described with respect topreferred embodiments thereof, it should be understood by those skilledin the art that the foregoing and various other changes and omissions inthe form and detail thereof may be made therein without departing fromthe spirit and the scope of the invention.

Having thus described typical embodiments of our invention, that whichwe claim as new and desire to secure by Let ters Patent of the UnitedStates is;

1. A semiclosed cycle, flowing gas laser system for producing an outputof laser energy, said system utilizing an electric discharge excitedmixing laser and chargeable with an initial charge of a mixture gaswhich includes an energizing gas and a relaxant gas, said systemcomprising:

a source of laser gas which is stored under pressure in a liquid state;

means connected to the laser gas source for expanding the liquid to format least some laser gas;

means for electrically exciting said mixture gas;

a laser chamber comprising;

a. an inlet means for admitting said excited mixture gas into saidchamber;

b. means for admitting laser gas into said chamber and for admixing thelaser gas with the excited mixture gas in the chamber to form a gasadmixture and at ieast a population inversion in said laser gas; and

c. outlet means for permitting the exhaustion of the admixture from thelaser chamber, laser gas removal means, positloned between the laserchamber outlet and the excitation means for removing the laser gascontained in the exhausted admixture and discarding the removed lasergas from the system, said removal means having heat exchange means forreceiving cool laser gas from said laser expanding means and fortransferring heat from said removal means to said cool laser gas;

means for conducting the cool laser gas through said removal heatexchange means to said laser chamber admixing means;

means including a compressor means for;

a. exhausting said admixture from said chamber outlet means and movingsaid admixture to said removal means; and

b. moving said mixture gas from said removal means through saidexcitation means and into said chamber inlet means; and

optical means positioned about said laser chamber for at least couplinglaser radiation from said chamber.

2. The system according to claim 1 including a first heat exchanger inthe admixture flow between the compressor means and the laser gasremoval means wherein the means for conducting the laser gas from theexpanding means to the admixing means include means for conducting lasergas from the source through said first heat exchanger and then to theadmixing means.

3. The system according to claim 2 including a second heat exchanger inthe admixture flow between the outlet means and the compressor meanswherein the means for conducting the laser gas from the first heatexchanger to the admixing means includes means for conducting the lasergas from the first heat exchanger through the second heat exchanger andthen to the admixing means.

4. The system according to claim 2 including a turbine expanderconnected to the flow of laser gas between the first heat exchanger andthe admixing means, the turbine expander being rotated by a pressureexpansion of the laser gas.

5. The system according to claim 4 including means for applying heat tothe laser gas at the input to said turbine expander.

6. The system according to claim 3 including a turbine expanderconnected to the flow of laser gas between the first heat exchanger andthe admixing means of said gas laser, said turbine expander beingrotated by a pressure expansion of the laser gas.

7. The system according to claim 6 including means for applying heat tothe laser gas at the input to said turbine expander.

8. The system according to claim 1 including a turbine expanderconnected to the flow of laser gas between the laser gas removal heatexchange means and the laser chamber admixing means.

9. The system according to claim 8 including means for applying heat tothe laser gas at the input to said turbine expander.

10. The system according to claim 3 including a turbine expanderconnected to the flow of laser gas between the laser gas removal meansand the admixing means, the turbine expander being rotated by a pressureexpansion of the laser gas, said turbine expander driving saidcompressor.

11. The system according to claim 10 including means for applying heatto the laser gas at the input to said turbine expander.

12. The system according to claim 1 wherein the compressor is coupled toa turbine driven by a gas flow from the source of laser gas.

13. The system according to claim 1 wherein the compres sor includes aprime mover which is supplied energy from a source outside of the lasersystem.

1. A semiclosed cycle, flowing gas laser system for producing an outputof laser energy, said system utilizing an electric discharge excitEdmixing laser and chargeable with an initial charge of a mixture gaswhich includes an energizing gas and a relaxant gas, said systemcomprising: a source of laser gas which is stored under pressure in aliquid state; means connected to the laser gas source for expanding theliquid to form at least some laser gas; means for electrically excitingsaid mixture gas; a laser chamber comprising; a. an inlet means foradmitting said excited mixture gas into said chamber; b. means foradmitting laser gas into said chamber and for admixing the laser gaswith the excited mixture gas in the chamber to form a gas admixture andat least a population inversion in said laser gas; and c. outlet meansfor permitting the exhaustion of the admixture from the laser chamber;laser gas removal means, positioned between the laser chamber outlet andthe excitation means for removing the laser gas contained in theexhausted admixture and discarding the removed laser gas from thesystem, said removal means having heat exchange means for receiving coollaser gas from said laser expanding means and for transferring heat fromsaid removal means to said cool laser gas; means for conducting the coollaser gas through said removal heat exchange means to said laser chamberadmixing means; means including a compressor means for; a. exhaustingsaid admixture from said chamber outlet means and moving said admixtureto said removal means; and b. moving said mixture gas from said removalmeans through said excitation means and into said chamber inlet means;and optical means positioned about said laser chamber for at leastcoupling laser radiation from said chamber.
 2. The system according toclaim 1 including a first heat exchanger in the admixture flow betweenthe compressor means and the laser gas removal means wherein the meansfor conducting the laser gas from the expanding means to the admixingmeans include means for conducting laser gas from the source throughsaid first heat exchanger and then to the admixing means.
 3. The systemaccording to claim 2 including a second heat exchanger in the admixtureflow between the outlet means and the compressor means wherein the meansfor conducting the laser gas from the first heat exchanger to theadmixing means includes means for conducting the laser gas from thefirst heat exchanger through the second heat exchanger and then to theadmixing means.
 4. The system according to claim 2 including a turbineexpander connected to the flow of laser gas between the first heatexchanger and the admixing means, the turbine expander being rotated bya pressure expansion of the laser gas.
 5. The system according to claim4 including means for applying heat to the laser gas at the input tosaid turbine expander.
 6. The system according to claim 3 including aturbine expander connected to the flow of laser gas between the firstheat exchanger and the admixing means of said gas laser, said turbineexpander being rotated by a pressure expansion of the laser gas.
 7. Thesystem according to claim 6 including means for applying heat to thelaser gas at the input to said turbine expander.
 8. The system accordingto claim 1 including a turbine expander connected to the flow of lasergas between the laser gas removal heat exchange means and the laserchamber admixing means.
 9. The system according to claim 8 includingmeans for applying heat to the laser gas at the input to said turbineexpander.
 10. The system according to claim 3 including a turbineexpander connected to the flow of laser gas between the laser gasremoval means and the admixing means, the turbine expander being rotatedby a pressure expansion of the laser gas, said turbine expander drivingsaid compressor.
 11. The system according to claim 10 including meansfor applying heat to the laser gas at the input to said turbineexpander.
 12. The system according to claim 1 wherein the compressor iscoupled to a turbine drivEn by a gas flow from the source of laser gas.13. The system according to claim 1 wherein the compressor includes aprime mover which is supplied energy from a source outside of the lasersystem.